Thiazyl sulfenamides



Patented Jan. 18,1949

i f-lomo@ Maintaining@ ggxzigjnal applicati@ May 26, 19213, i

s'egriallfin.fiassay piviaed and this applica-L y tion.Januaryjzgillli, Serial No. 4,075

Thisinvention relates to a new class ofbhmlal compounds Wlricli-` arer valuable aocelerators of' the Vulcanization of rubber or rubber-like substances. l

This application-.isiv a divisionof our copending application Serial No.y 488.3555, lled May 26,1943, now Patent Nol 2,445,722l

It is a prirnary `object of the: present invention to provide a newnclass ofrehemical cornpgu-nds. Another object is to provide a new. claSS 01l improved rubber vulcanization accelerator-soi the delayed-action, non-scorching type; Y

The above and further objectsiwilltbemanliest in the description of the invention which follows.

of chemical compounds are Very effective in accelerating the vul'cani'zation' of natural or synthetic rubber., The4 new. compounds may. be. conveniently prepared( by oxidizing a mixture., ojfa vii.

non.- arylenei 2ni,er captothiaz ole, andanlnlbna or.. gg

hours, the reaction v,solution being maintained atl y tainedlas l0 gra sof ..21 y, 100 4 grains' ochloroa'cetone was pmtrecll lon to l 119: grams of 'ammonium dithiocarbaniatej (prep pared from ammonia and carbon disulfide)-`Iv` ina. 2-liter Erlenrneyer flask. The resulting mixture s consisted ofz two;phases, the ether solution of chloi'ofacetoiie andfthe solid phase of-ammonium dithiocarbarnate.. In the course of"15 minutes the ether begarrtoboil. The reaction was Vigorl ous for an -hour andthien subsided'. Theniixture several hours-:and then;was:flteretily The;lt'rte;A a light yellow ether solution, was evaporated' on a steamv bathto leave a residue of a dark brown imei. f.chfsolidifedupmooolin 'fr 'rhersoiid It has-been found that members of a new'class d Wm S -dilutecsodiumbydnogsme solid, A2.dimitealito-y4..methylthiiallblelf wasn ab 'tainedinexi'yield-.ot` '78l'g11amsa ,i An aqueous solution was prepared. containing 3x. grams of the mercaptotlfxiazole,.. .Qfz;

cyclohexylamiinef and ltigramsoff sodium hadron.

-ide infanvolume-zofooi mir. manoaqueous-riodinei v solutiongcontaining "wfgrams otiilodme' amii 66* grams-of "potassium iodide@ inf a{ volume ofl G50-mls;

zole and amine, with; stirring; over aperitief erf-'two a temperature of 340" "The'solid product wehe-.precipitated trom, thefreabtion. mixture was.Separatedandgdrde 'Il'1i`s.product Nylb: bwl (fl-rnethahfthi i simenon-mams. au,

possesses the following; formular:

vorrei-'ein Ri' and R2 are hydrogen or alliyliraaltcwlfs;`

at least one" `of said R1- an-d" Re being#tv antifa/limb radical; and Rais'v hydrogen, an radcalon a cyclo-alkyl radical. Thus,-theneweeomqwundsf are derivatives of sulfenamide (HSNHz) ExamplesA of alkyl and cyclo-alkyl. radicals includeK methyhethyl, propyl, ,butyl; amyl, hexyl, heptyl,

r nina-tio accelerator by'Ycornpairing,` itf Wittli--ftl'ierv` 4'5 standard'accelerators.mercaptobenzotliiazole and@ dream-061mm drsulnde" the; latter being a,

layed-action accelerator,` i'n 'the follovt'fing 'rubber octylgdecyl; lauryl, cyolohexyl, methylcyclohexyl, formula; benzyl and similar radicals. y y, v The following specie examples are presented 50 Irrgredients', Pants by Weight `for-illustrative purposes only; and are not to be construedv as limiting the invention thereto.

Example. 1

v n @reamfcolorei crystals-melts..- ingr at Qf-.lf Y sulenamide derivative'.

Samples of the three rubber compositions, so formulated, were heated for 30 minutes at 240 F. to determine Whether or not they possessed any tendency to pre-vulcanize or set-up during processing r`operations prior to time usual ,vulcanizing stepnd theiifolloviiilg physical tasting .data

were obtained:

Modulus of elasticity in St'rlelgtlllem Accelerator lbs./in. at lbs lin {at} elongation@ j ek o v v Y l.:

Mercaptobenzothiazole Dibenzothiazyl disulfide N-cyclohexyl (4-methyl-2-thiazyl) sulfenamide.

Other samples of the same rubber compositions were heated for 20 minutes at 280 F. to determinethe relative accelerating properties of the respectiveuaoceierators, .and thefollowing data were obtained:I i

Modulus of `Elas1: 1c1tyin Strllngstllllein Accelerator lbs./in.1.at lbs lin, at

elongation4 v mik Mercaptobenzothiazole 650 2.550 Dibenzothiazyl disulfide. 525 2,450 N-cyclohexylf (4i-methy1-2-thiazy1) 1,675 f 3.775

Sulfemmide r o Vv`iThe vtwo sets of testing data given above show thatthe vsulien'amide derivative from cyclohexylamine andl 2-mercapto-i-methylthiazole is an excellentdelayed-action acceleratonsince the rubber composition includingit did not vulcanize at therelatively low vulcanizing temperature of 240 F. (which is often reached. during-factory .processingfof .arubber composition), in contrast with the composition including the 'standard accelera-` tor, f: mercaptobenzothiazole. Furthermore,thel newaccelerator imparted very high physical propf ertiesrto therubber composition after a shortcure at :28.0"?,F., -in comparison with mercaptQbenzo--- thiazole and the standard delayedac yfony accel-r;`

erator, libenzothiazyldisuliidei mainte? i Ammonium dithioc'arbamate was co'ridex'isec'i witheehiomizmutanonei (B. P; 11a-116 c., sep; a'rated` bydistillation" from a commercial sample` of Vlshlo'rinated frnethyl,A ethyl ketone) to produce Zimereapto 4,'5 dimethylthiazole (light yellcivv crystals, melting?atf162--l63uw C.) 'in a manner sinifl'- ilar to the preparation of 2mercapto4methyl thiazole from'chloro-acetone, describedf'in Example 1. An aqueous solution comprising four moles of cyclohexylamine, one mole of the 2-rnercapta-4,5-dimethylthiazole and two moles of sodilimhydroxide was oxidized at 8 -10f by an iodine-potassium iodide solution` to producea 9 3 per' cent, y ie1d`(based upon the thiazole) of N- havingtlie iollowin'gformula: i

CH3-CHI above sulfenamide was obtainedas white, glistening,` crystalline leaflets, melting at v{l2- 947.9

In a similar manner, a solution of ten moles of isopropylamine, one mole of 2-mercapto-4,5di methylthiazole and two moles of sodium hydroxide Was oxidized by iodine to produce a yield of 80 per.,cen;t M Nisoprgpyl vv(4,35,-dimethyl-Z-thiaa'yl) fsulfeamidegghavi gt he followingifrmula:

HxC-C-N /C-S-N-CH-CHs s Ha y i'soiirfoplll'd-ru vative was obtained as a white, crystalline solid; ,melting at 62-63 C.

The abovetwo derivatives of 4,5-dimethyl-2- ,thiazyl-'sulfenamide'lwere tested as vulcanization 4accelerators"injthe'rubber formula set out in Example 1'." No'vulc'anzation resulted on heating the .compositions containing the sulfenamide derivatives for 30 minutes` at 240 F. On heating thg'rubber compositions for 20 v and 40 minutes at 280i` E, the following data were obtainietig.k

amide having theffollovving formula:

i This smfenamidderivativewas obtainedif'sfa soft, tan-colored solid, melting lat 6568 "Cf *The* new compound was tested as aivulcanization accelerator in theru-bber formula set out in Example 1. No vulcanization occurred on heating the composition for 60 or 80 minutes at 240 F., indicatingtliat the oo mpoundis an -extremelyisafef delayed: action; accelerator. Whenfthe composi-y: tion was heated 40 andivminutesgat280'F.

Example 4 A Acommercial mixtureof l-chloro-Z-butanone and3chloro2butanone (approximately one part tor three parts, respectively, produced by chlorin ating methyl, ethyl ketone) was condensed with ammonium dithiocarbamate to forma solid mixturet-ofV 2-mercapto-4-ethylthiazole and 2mer capta-4, y5dimet,hyltliia-zole. An .aqueous solution ycontaining 145 grams of the mixed thiazoles (90;percent pure), 80 grams of sodium hydroxide and 250 grams of cyclohexylamine in a volume of ve liters was cooled in an ice bathand oxidized by a ymixture of chlorine gas and air, passed into the agitated solution during the course of three hours.` The product, a mixture of about one` part of N-cyclohexyl (Ll-ethyl-Z-thiazyl) sulfenam'ide and three parts of N-cycl-ohexyl- (4,5-dimethyl-2- thiazyl) sulfenamide, precipitated as a soft, tan solid, in a yield of 165 grams (78 per cent) mel-tv ing at about 5'7-77 C. The mixture of sulfenamides Was tested in the standard accelerator test formula shown in Example 1. No vulcaniaaticn occurred on heating the rubber composition for 60 minutes at 240 F. On heating the rubber composition for and 60 minutes at 280 F., the following data were obtained:

Fifty ml. of 5.5 per cent sodium hypochlorite solution were added to 100 ml. of concentrated ammonia containing grams of cracked ice. To the resulting solution there was gradually added, with stirring, 10.5 grams ci 2mercapto4,5di methyl-thiazole dissolved in a solution of 5.52 grams of sodium hydroxide in 100 ml. of Water.

After the addition of a portion of the thiazole solution a occulant precipitate appeared, which soon became very bulky in the reaction vessel. The mixture was stirred for a short time after the addition of the entire quantity of the thiazole solution. Then the White, crystalline precipitate was separated, washed with Water and dried. The product, 4,5dimethylthiazylsulfenamide,

BeC-C-N \\CS-NH2 Hao-o-s is an eiective rubber vulcanization accelerator of the delayed-action type, being similar in accelerating activity to the alkyl and cyclonalkyl derivatives specically described above.

Example 6 Various primary amines were separately reacted with 2-mercapto-4,5-dimethylthiazole by oxidation of an alkaline aqueous mixture of one mole of the thiazole and ve moles oi the amine by means of an aqueous iodine-potassium iodide solution.

mula:

deriva N-meythlisobutylcarbin (4,5-dirnethyl-thiaayl) -sulfenarnidey In-a"'similar manner iveV moles -ofsee-amyl-` aminei-(met'hyl-npropylcarbinarnine were-treat#- ed with iodine in the .presence of far-1 alkaline"'sobreKV tion o'ffonemole of 2-lmercapto-fl-ethylthiaaoleto produce "Ni-secr amyl ("lethyl-2-thiazylll suli-:n'fv amide-or N-'methyll-mpropylcarbin (methyl-2L? thiazyll'sul-fenamide,I having the-'following for?y The `yields vand melting.. points of the. sulte'nfA amide. gdyerivfativces'so produced are set .outin the following tabler. l Y

'1 2-Tliiarylsulfenaniidc Point 51-52 C 40-42 C (liquid) (liquid) N Sec. amyl-4ethyl Each of the four above sulfenamide derivatives was tested in the rubber accelerator test formula of Example 1, and were found to cause no Vulcanization of the rubber when the latter was heated for 60 minutes at 240 F. When the rubber compositions were heated for 40 and 60 minutes at 280 F., the following data were obtained:

The various members of the new class of chemical compounds are equally eiective delayedaction vulcanization accelerators in rubber tread compounds, latex compounds or -other conventional types of vulcanzable compounds of rubber, reclaimed rubber, or synthetic rubber, and

consistently produce rapid-curing compositions, which in the vulcanized state possess unusually high modulus, tensile and :abrasion-resisting properties. The various synthetic rubbers vulcanizable by heating with sulfur are herein considered equivalent to rubber, examples being butadiene polymers, isoprene `polymers and various interpolymers of conjugated diolens and vinyl compounds, such as Buna S (copolymer of butadiene and styrene) and Buna N (copolymer of butadiene :and acrylonitrile). Although sulfur has hereinabove been mentioned as the preferred vulcanizing agent, other known vulcanizing agents susceptible to acceleration are contemplated.

The preferred class of sulfenamide derivatives may be prepared by other methods than those mentioned above. For example, a mixture of a non-aromatic mercaptothiazole and ammonia or a primary amine may beoxidized by hydrogen peroxide or other oxidizing agent. The invention is not limited to derivatives prepared in accordance with any particular method, but includes the preferred cl-ass of compounds, however they may have been formed. b y l In .addition to the above-enumerated desirable properties imparted by the new accelerators to rubber compositions, it has been found that the vulcanized compositions also are highly efficient, having low hysteresis characteristics. When compared to conventionally accelerated vulcanized rubber compositions, the new compositions are found to be .unusually resistant to deterioration upon flexing or aging. l f

Conventional accelerator activators Y may be employed to an advanatge with the new class lof accelerators when extremely rapid .vulcanization is desired, especially at lower temperatures. Also,

the new accelerators may -be used in combinationv with other accelerators, such asa guanidine (e. g.. diphenyl guanidine) or :a conventional mercaptothiazole derivative (e. g., mercaptobenzothiazole `le of this patent:

8?, or dibenzothiazyl disuldeL-'i'n order to produce rubber compositions having especially rapidor specific vulcanizing properties. The -newjk accelerators may be employed in other proportions than the proportion shown, but will normally be utilized in the range of 0.1 to l0 parts perflOO amide and N-cyclohexyl (4,5-dimethyl-2-thia'zyD sulfenami-de.

4. A substance having the formula,

R1-C-N\ wherein R1 and R2 are selected from the group consisting of hydrogen and alkyl radicals, at least one of said R1 and Rg being an alkyl radical, and R3 is one of thel group consisting of hydrogen, 'alkyl radicals and cyclo-alkyl radicals.

GEORGE E. P. SMITH, Jn. EDWARD L CARR.

REFERENCES CITED The following references are of record in the UNITED STATES PATENTS Name Date Carr et al July 20, 1948 Number Certificate of Correction Patent No. 2,459,736. January 1s, 1949'. GEORGE E. P. SMITH, JR., ET AL.

It is hereby certified that errors appear in the printed specication of the above numbered patent requiring correction as follows:

Column 7, line 36, for advanatge read advantage column 8, line 42, list of references cited, for the patent number 2,445,772 read 2,445,722;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oice.

Signed and sealed this 13th day of September, A. D. 1949.

JOE E. DANIELS,

Assistant Gommzaaoner of Patents. 

